Enumerable.LongCount(Of TSource) Method (IEnumerable(Of TSource), Func(Of TSource, Boolean))
Returns an Int64 that represents how many elements in a sequence satisfy a condition.
Assembly: System.Core (in System.Core.dll)
'Declaration <ExtensionAttribute> _ Public Shared Function LongCount(Of TSource) ( _ source As IEnumerable(Of TSource), _ predicate As Func(Of TSource, Boolean) _ ) As Long 'Usage Dim source As IEnumerable(Of TSource) Dim predicate As Func(Of TSource, Boolean) Dim returnValue As Long returnValue = source.LongCount(predicate)
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Collections.Generic.IEnumerable(Of TSource)
An IEnumerable(Of T) that contains the elements to be counted.
- predicate
- Type: System.Func(Of TSource, Boolean)
A function to test each element for a condition.
Return Value
Type: System.Int64A number that represents how many elements in the sequence satisfy the condition in the predicate function.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable(Of TSource). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is Nothing. |
| OverflowException | The number of matching elements exceeds MaxValue. |
The following code example demonstrates how to use LongCount(Of TSource)(IEnumerable(Of TSource), Func(Of TSource, Boolean)) to count the elements in an array that satisfy a condition.
Structure Pet Public Name As String Public Age As Integer End Structure Sub LongCountEx2() ' Create a list of Pet objects. Dim pets As New List(Of Pet)(New Pet() _ {New Pet With {.Name = "Barley", .Age = 8}, _ New Pet With {.Name = "Boots", .Age = 4}, _ New Pet With {.Name = "Whiskers", .Age = 1}}) ' Determine the number of elements in the list ' where the pet's age is greater than a constant value (3). Const Age As Integer = 3 Dim count As Long = _ pets.LongCount(Function(pet) pet.Age > Age) ' Display the result. MsgBox("There are " & count & " animals over age " & Age) End Sub ' This code produces the following output: ' ' There are 2 animals over age 3
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The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.